Analysis of 851 urine samples for iodine Insufficiency and pregnancy urinary Iodine concentrations from LIFE cohort. Use HPLC and mass spectrametry Using state of the art laboratory techniques, High Performance Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometry (HPLC-ESI-MS/MS), the laboratory will measure urinary iodine concentrations in 501 female baseline samples and 350 pregnancy samples. The information needed to identify these samples will be provided by NICHD. This work will be performed according to the standard operating procedures supplied by the laboratory to NICHD. It will include continuing quality control and quality assurance procedures. One mi. of urine per sample will be provided for this task.